1. Field of the Invention
The present invention relates to an electric disk brake where a brake pad is pressed toward a disk rotor by means of an electric motor so as to generate braking force.
2. Description of the Related Art
In a generally known electric disk brake, rotary motion of a rotor of an electric motor is converted into linear motion for a piston by using a rotary-to-linear conversion mechanism such as a ball-screw mechanism or a ball-ramp mechanism, whereby two brake pads are pressed toward a disk rotor to generate braking force. In the electric disk brake, by detecting value of pedal efforts (or displacement) of a driver, etc. with a sensor, rotation of the electric motor is controlled with a control device based on the value detected so as to generate a given braking force.
In this kind of the electric disk brake as disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-173691 (hereinafter referred to as the Patent Document 1), a reduction mechanism using a spur gear, etc. is interposed between a rotary-to-linear conversion mechanism and an electric motor. With this reduction mechanism, it is possible to reduce load applied to the electric motor contributing to downsizing as well as energy saving for the electric motor. Further, the Patent Document 1 discloses art where a pair of rotary-to-linear conversion mechanisms is driven with a single electric motor.
However, in the conventional electric disk brake using the reduction mechanism as discussed hereinabove, there has been a problem that the reduction mechanism needs to be large in its size in case a speed reducing ratio is enlarged. Further, if the electric disk brake is used with the pair of rotary-to-linear conversion mechanisms, output expansion cannot be achieved.